Converters for converting the output voltages of AC or DC sources into a voltage having a particular desired value are well-known. For example, laptop computers and the like commonly use such a power converter which plugs into a common wall outlet and electrically connects to the laptop computer. A step-down transformer and rectifying circuit are typically disposed within a housing to which the power plug is attached to facilitate electrical interconnection with the wall outlet. A filtering circuit may also be disposed within the housing.
Also, adapters or power converters for facilitating the use of laptop computers and the like from 12 volt DC sources, i.e., in automobiles, boats, etc., are likewise well-known. Such power converters contain the necessary circuitry for converting the 12 volt DC source voltage to a voltage suitable for powering the electrical device.
Unfortunately, the fact that there are many such electronic devices operating at many different voltages makes it difficult to provide a small number of power converters capable of servicing them all. The great diversity of such electronic devices requires that a large number of different power converters be provided. Each device typically has its own unique power requirements. As such, a power converter specifically intended for use with a particular electronic device must typically be provided therewith.
Also, it is similarly necessary to purchase a compatible, i.e., having the correct output voltage, substitute power converter when a replacement is required. The proliferation by different output voltages provided by different power converters makes it extremely difficult to maintain a wide selection of such power converters for use as replacements.
In an attempt to alleviate the above-mentioned deficiencies, prior art devices have been constructed so as to provide selectable output voltages. Such prior art devices utilize a switch formed thereon for facilitating selection of the desired output voltage. However, the use of such a switch inherently makes it possible to select an incorrect output voltage. The selection of such an incorrect output voltage may potentially damage the device powered thereby. This is particularly true if the incorrectly selected output voltage is higher than that required by the device powered thereby. The incorrect output voltage may be inadvertently selected by the user prior to utilizing such prior art selectable output voltage power converters or, alternatively, may accidentally be changed, i.e., via mishandling, after use thereof has commenced.
The output power selection switches of such prior art power converters are oftentimes difficult to read and/or set. This is, in part, due to the miniaturization of such devices, which requires such switches and their associated indicia be formed as small as possible. Thus, it is not uncommon for a user to inadvertently select the power output setting adjacent the desired setting.
One example of such a prior art selectable power converter is the Model MW182 800 mA Regulated DC Adapter manufactured by Minwa of Taiwan. This device provides the ability to convert the power output from a car cigarette lighter, i.e., 12 volts DC, to any one of the following outputs: 1.5, 3, 4.5, 6, 7.5 9, or 12 volts DC.
Although such power converters have proven generally suitable for their intended purposes, they possess inherent deficiencies which detract from their overall effectiveness in the marketplace.